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Manual Dosage Calculation Guide

🧮 Use Our Interactive Calculator

For easier and safer calculations, try our Interactive Reconstitution Calculator that:

  • ✅ Does all the math automatically
  • ✅ Shows visual syringe guides
  • ✅ Generates a printable reference card
  • ✅ Handles all peptide types (Semaglutide, Tirzepatide, Retatrutide)

Why Learn Manual Calculations?​

While our interactive calculator handles the math automatically, understanding the underlying formulas helps you:

  • Verify calculator results - Double-check any calculation tool
  • Calculate without internet - Use these formulas anywhere
  • Understand the science - Know exactly what's happening with your medication
  • Catch potential errors - Recognize when something doesn't look right
Critical Safety Warning

Accurate math is non-negotiable. A misplaced decimal can deliver ten or even one hundred times the intended dose and may be life-threatening.

  1. Always double-check calculations
  2. Use multiple verification methods
  3. If anything is unclear, do not inject

The Three-Step Manual Calculation Process​

Here's how to calculate your dose manually. This is the exact same math our calculator uses behind the scenes.

1. Find the concentration of your mixed solution​

You need:

  • Total peptide in the vial (mg)
  • Total BAC water added during Reconstitution (mL)

Formula

Concentration (mg/mL) = Total Peptide (mg) / BAC Water Added (mL)

Example

Vial contains 10 mg
BAC water added = 2 mL
Concentration = 10 mg / 2 mL = 5 mg/mL

Because 1 mg = 1000 mcg, 5 mg/mL equals 5000 mcg/mL.

2. Work out the volume (mL) for your target dose​

Formula (mg)

Injection Volume (mL) = Desired Dose (mg) / Concentration (mg/mL)

Formula (mcg)

Injection Volume (mL) = Desired Dose (mcg) / Concentration (mcg/mL)

Example

Desired dose = 2.5 mg
Concentration = 5 mg/mL
Injection Volume = 2.5 mg / 5 mg/mL = 0.5 mL

(The same answer appears if you use micrograms.)

3. Convert mL to insulin-syringe Units​

U-100 insulin syringes hold 100 Units per mL.

Formula

Injection Volume (Units) = Injection Volume (mL) × 100

Example

0.5 mL × 100 = 50 Units

Draw the solution to the 50-Unit mark on a standard U-100 syringe to deliver a 2.5 mg dose.

Verifying Your Calculations​

Quick Verification Checklist​

✅ Units Check: Ensure your final answer is in "units" not "mL"
✅ Reasonableness Check: Most doses require 5-100 units
✅ Double Calculate: Do the math twice, preferably with different methods
✅ Compare with Calculator: Use our interactive calculator to verify

Common Red Flags​

🚩 Needing more than 100 units (requires multiple syringes)
🚩 Extremely small amounts (less than 5 units is hard to measure accurately)
🚩 Results that don't match typical dosing ranges for your peptide

Pro Tip

Many users find it helpful to create a reference card with their specific calculations once verified. Our interactive calculator can generate this for you automatically!

When every number checks out, continue to Drawing & Injecting.

Peptide-Specific Manual Calculation Examples​

These examples show manual calculations for common scenarios. Remember, our interactive calculator does this automatically for all peptides.

Example 1: Standard Concentration (10mg/mL)​

Setup:

  • 10mg vial of retatrutide
  • Add 1mL BAC water
  • Concentration = 10mg/mL

Common Doses:

For 2mg dose:    2mg ÷ 10mg/mL = 0.2mL = 20 units
For 4mg dose:    4mg ÷ 10mg/mL = 0.4mL = 40 units
For 5mg dose:    5mg ÷ 10mg/mL = 0.5mL = 50 units
For 7.5mg dose:  7.5mg ÷ 10mg/mL = 0.75mL = 75 units
For 10mg dose:   10mg ÷ 10mg/mL = 1mL = 100 units

Example 2: Diluted Concentration (5mg/mL)​

Setup:

  • 10mg vial of retatrutide
  • Add 2mL BAC water
  • Concentration = 5mg/mL

Common Doses:

For 2mg dose:    2mg ÷ 5mg/mL = 0.4mL = 40 units
For 4mg dose:    4mg ÷ 5mg/mL = 0.8mL = 80 units
For 5mg dose:    5mg ÷ 5mg/mL = 1mL = 100 units
For 7.5mg dose:  7.5mg ÷ 5mg/mL = 1.5mL = 150 units*
For 10mg dose:   10mg ÷ 5mg/mL = 2mL = 200 units*

*Note: Doses requiring >100 units need multiple injections or a larger syringe

Why Manual Calculation Knowledge Matters​

Understanding these calculations empowers you to:

  1. Cross-verify any tool or calculator - Technology can fail or have bugs
  2. Help others safely - Share knowledge in communities
  3. Recognize dosing errors - Spot mistakes before they happen
  4. Adapt to different scenarios - Handle unusual vial sizes or concentrations
Remember

The math isn't complicated - it's just division and multiplication. The key is being careful and methodical. Our interactive calculator automates this process while showing you exactly what it's calculating.

Additional Resources​

By Mr Fox
Published April 17, 2025